We played a game yesterday where we came to the conclusion that the thief could use his action "climb" to move one space, even if he had used all of his actual movement points with the interpretation that "cross one wall" meant that he automatically moved to the square on the other side.

Unfortunately this allowed the thief to move CRAZY distances without little effort. Is this a correct interpretation? It basically allowed the thief to run to a treasure and back to the opening in one move without any way for us to stop him.